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I guess your client would rather have a wizard to guide him throughout the installation process. Also, if you are talking about Desktop Applications you could configure your wizard to perform custom actions such as configure a database or connect to a licensing server.

This is a miniature version of the debate of "Why use an IDE, I love writing code in a text editor."

One benefit of a wizard is that sometimes you might be able to save ftp credentials, for instance. Then again, if you are on a local network and you don't have to login, or you have some other way of caching credentials, (like using FileZilla), the small amount of time that you save may be so small that it really doesn't matter.

In general, another reason that wizards may be helpful is when they provide a small set of recently used options/servers/connections/tables/folders in a dropdown that you can choose from instead of having to type them in again or navigate to them again.

Cons to wizards: You can get too reliant on them. You can lose settings if they get mysteriously reset somehow, so if you do use them, remember to keep notes of how you set up a wizard or how you typically use it.

Same goes for using an IDE. If you always open your solution on your machine, make sure to open it every once in a while on a new machine just to check that there is not some magical/transient/volatile setting that is set correctly on your machine, either in the registry or in the solution/project properties, a plugin, your .suo, etc.

Installation Wizards are nice for users, and you can wrap lots of other little changes like automatic unpacking, changes to the registry, tons of stuff.

Also a major reason to use something like InstallShield is that the initial perceived installation speed versus a free wizard is going to be faster. Also, use legitimate 3rd party signing of your executable so that Windows doesn't popup Unknown Publisher (it looks sketchy).